December 22, 2009
Photographer: Christine Churchill
Summary Author: Christine Churchill; Jim Foster
The photo above shows a curious, cirrus Christmas tree trimmed in white, decorating the northern California sky. This wispy "tree" even looks a bit like it has a small star at the top. Cirrus clouds are referred to as "mares’ tails" since their wind buffeted edges look like strands of a horse's tail. Of course, from different perspectives they can take on the appearance of any number of objects. This is due to a psychological phenomenon known as pareidolia. Cirrus clouds are composed of ice crystals, ranging from about 0.01 to 0.1 mm in diameter, and form in the mid and upper reaches of the troposphere. In this photo these ethereal clouds are shaped by strong upper atmospheric air currents, including jet streams, that quite easily split and stretch them. Photo taken in August 2009.